1. Field of the Invention
This invention relates to computer systems. More particularly, this invention relates to detecting a cooling device in a computer system.
2. Description of the Related Art
As CPUs and other components such as hard disks and graphics processors increase their operating frequency, they consume more power and consequentially generate more heat. At the same time, increased transistor density has also caused some components to produce more heat. Because components are designed to operate within a certain temperature range, this increased heat generation may cause many problems. Many errors can occur once a component begins to overheat. For example, system crashes, random reboots, and system lockup are common errors caused by an overheating processor. Furthermore, extended high temperatures may damage the components themselves. Thus in modem computer systems, specialized cooling systems are required to prevent heat-related problems.
With earlier components, all that was needed to adequately dissipate heat may have been a passive heat sink attached to the component. A passive heat sink is simply a piece of metal attached to the component in such a way that it draws heat away from the component and radiates this heat into the surrounding air. As components began generating more heat, fins were added to heat sinks. Fins increase the surface area of a heat sink, allowing the heat sink to radiate more heat. A fan placed somewhere in the computer case assists passive heat sinks by circulating cooler air across the heat sink, allowing more heat to be radiated away. Most computer systems include, at a minimum, one or more passive heat sinks and a fan located somewhere in the case. Some computer systems may contain other cooling devices in addition to or instead of fans and/or passive heat sinks. In any computer system, failure of a cooling device may result in one or more of the system components overheating.
For some newer components, a passive heat sink may no longer satisfactorily remove enough heat. For example, many newer processors require active heat sinks. An active heat sink is a passive heat sink connected to a dedicated fan or other active cooling device. The fan is attached so that it blows directly over the heat sink to provide additional cooling. Some heat sinks also include a Peltier cooler, which is a solid-state device that pumps heat from one of its sides to the other. Including a Peltier cooler may increase cooling of a particular component, but the Peltier element may also increase the overall heat generated in the system.
While an active heat sink configuration may be capable of radiating enough heat away from the component to prevent overheating, it also has its drawbacks. Like all active components, active cooling devices such as fans may be susceptible to failure. Fans used in computer systems are often inexpensive and unreliable, making them even more likely to malfunction. If a cooling device such as a fan or a Peltier cooler does malfunction, active heat sinks are often incapable of adequately cooling the component anymore. This may happen because the metal heat sink is smaller than it would have been if it had been designed to be used without the cooling device. Additionally, since other cooling measures such as the system fan were no longer as necessary to cooling that particular component after the addition of the dedicated cooling device, the other cooling measures may have been placed so that they no longer directly cool the active heat sink. In heat sinks incorporating Peltier coolers, the extra heat generated by the Peltier element creates an even greater risk to the component if the fan or other cooling device fails.
Thus, when operating properly, heat sinks, fans and other cooling devices can usually prevent heat-related problems from endangering system performance and components. However, as mentioned above, cooling devices such as fans may not always be very reliable components, and cooling device failure may endanger components and may also have detrimental effects on system performance. Prior art systems have recognized this possibility. For example, alarm circuits that detect processor overheating are available. These alarm circuits may monitor the processor fan power supply, the temperature of the processor, or the airflow through a fan that cools a processor. These circuits are configured to generate an alarm when they detect a condition that may lead to processor overheating.
Alternately, some systems have tried to avoid relying on active cooling devices at all, opting instead for purely passive heat sinks. This option is limited. For example, many computer systems are being designed to fit inside smaller cases, so there may be limits on the extent that a passive heat sink""s surface area can be increased. When a heat sink""s surface area is limited, the amount of heat it can dissipate is correspondingly limited. Also, many case and/or motherboard configurations place the power supply fan too far away from or facing in the wrong direction of the heat sink needing air circulation. Because there is little airflow over the heat sink, its heat radiating abilities are further limited. Because of these limits, many newer components can no longer be adequately cooled without an active heat sink or cooling device.
As discussed above, cooling device failure is an important concern in a computer system. If a cooling device fails, components may not be properly cooled. Expensive components such as the processor may overheat, causing unreliable performance and possibly even destroying the components themselves. Even if the component is only connected to a passive heat sink, the passive heat sink may depend on a different cooling device such as a fan used to cool a power supply to circulate enough air across the heat sink or to otherwise allow the heat sink to adequately draw enough heat away from the component.
Various embodiments of a method and circuit for detecting a cooling device in a computer system are disclosed. In one embodiment, a computer system includes a cooling device configured to cool a component, a power supply configured to power the component, and a cooling device detection circuit configured to detect the cooling device. The cooling device detection circuit includes a detection stage and a power management stage. The detection stage is configured to detect the cooling device by sensing an indication that the cooling device is functioning. The power management stage is coupled to the detection stage and is configured to turn the power supply off if the cooling device is not detected.
In some embodiments, the cooling device may include a fan that is part of an active heat sink coupled to a CPU. Alternately, the cooling device may include a fan configured to cool a main power supply in the computer system.
The indication that the cooling device is functioning may, in some embodiments, include an indication that current is flowing across the cooling device. In some embodiments where the cooling device includes a fan, the indication that the cooling device is functioning may include a tachometer signal.
The power management stage may be configured to receive an input indicating whether the computer system is in a power conservation mode in one embodiment. The power management stage may, in some embodiments, receive an input indicating whether the computer system is requesting that the cooling device be turned off. If the computer system is in a power conservation mode or requesting that the cooling device be turned off, the power management stage may be configured to turn the cooling device off. The power management stage may receive an input indicating whether the voltages in the computer system have stabilized in some embodiments. The power management stage may turn the power supply off by deasserting a signal that controls the power supply. A south bridge may generate the signal.
In another embodiment, a method for detecting a cooling device in a computer system is disclosed. The method includes detecting the cooling device by sensing an indication that the cooling device is functioning and if the cooling device is not detected, turning off a power supply that provides a component cooled by the cooling device with power. The component being cooled may be a CPU. The method may also include sensing whether a plurality of voltages in the computer system have stabilized, sensing whether the computer system is in a power conservation mode, and/or sensing whether the computer system is requesting that the fan be turned off.
The indication that the cooling device is functioning may be sensed by sensing a current flowing from a ground terminal of the cooling device to ground in some embodiments. In some embodiments, sensing may include sensing a tachometer signal.
In one embodiment of a cooling device detection circuit, the circuit may include a current-detecting device configured to sense current flowing from a ground terminal of a cooling device to ground. The circuit may also include a signaling device configured to assert a detection signal if the current-detecting device senses the current and to deassert the detection signal if the current-detecting device does not sense the current. In some embodiments, the cooling device detection circuit may include a diode and a transistor. The diode may be coupled between a ground terminal of the cooling device and ground so that when current flows from the ground terminal to ground a voltage drop is produced across the diode. The transistor may be configured to turn on in response to the voltage drop being produced across the diode. The signaling device may include a transistor configured to turn on in response the current-detecting device sensing the current and to turn off in response to the current-detecting device not sensing the current in one embodiment. In one embodiment, the circuit may include an interface configured to generate an interrupt that causes an alarm.
In one embodiment of a fan detection circuit, the circuit includes a tachometer-detecting device configured to sense a tachometer signal provided by the fan. The circuit may also include a signaling device configured to assert a detection signal if the tachometer-detecting device senses the tachometer signal and to keep the detection signal unasserted if the tachometer-detecting device does not sense the tachometer signal. In one embodiment, the tachometer-detecting device may be configured to sense the tachometer signal by continuously monitoring the tachometer signal. In another embodiment, the tachometer-detecting device may be configured to sense the tachometer signal by latching a first pulse of the tachometer signal. In one embodiment, the fan detection circuit may include an interface configured to initiate an interrupt that causes an alarm if the detection signal is not asserted.